In the application of single-wall carbon nanotubes to nanodevices, to obtain device characteristics and stability, it is a very important subject to sort out nanotubes different in their electrical properties. Armchair carbon nanotubes all have metallic properties, and they are promising wiring materials for nanodevices.
For methods of selectively extracting metallic carbon nanotubes alone, Patent Document 1 discloses a technique where carbon nanotubes are irradiated with light of a single wavelength to excite carbon nanotubes in the specific electronic state, and the excited carbon nanotubes are burned away by oxidation with oxygen or any other oxidant.
Patent Document 2 discloses a technique where carbon nanotubes having non-uniform band gaps are irradiated with laser light in an atmosphere of oxygen to excite specific carbon nanotubes, and the excited carbon nanotubes are removed by oxidation.
Patent Document 3 discloses a technique where specific low-dimensional quantum structures are irradiated with electromagnetic waves and low-dimensional quantum structures having a density of states that resonate with the electromagnetic wave are selectively removed by oxidation. Further, Patent Document 4 discloses a method in which alternating voltage is applied to a carbon-fiber suspension to allow conductive fiber alone to adhere to the insulating film on electrodes.    Patent Document 1: Japanese Patent Laid-Open No. 2004-210608    Patent Document 2: Japanese Patent Laid-Open No. 2004-284852    Patent Document 3: Japanese Patent Laid-Open No. 2005-074557    Patent Document 4: Japanese Patent Laid-Open No. 2004-026595